Hello,For the Schema 20kW audio amplifier, you should discuss that schematic with its designer (Mr Glen Klienschmidt). According to Mr Glen, he was designed this power amplifier for experimental purpose only. He hasn't been tested nor made this amp....

It is also very optimistic to drive so many transistors in parallel and hope for good balance with only passive resistor balancing. One should be very careful to match all components around the transistors to the same value.